Have there been any cross promotional literature related to Bojack? I remember when Simpsons Mania ruled back in the early 1990's, and they would periodically release cross sectional books that explored the family's personal lives, as well as Springfield.
I think 4 seasons in, enough groundwork has been laid in terms of the show's mythos and world building to justify supplemental books. I know that DK publishing has done numerous guides based on Star Wars, James Bond, Marvel, and DC Comics, and have in recent years given the same myth worshipping treatment to a select group of video game franchises, the most recent being on the Assassin's Creed series.
I would love to see a DK Publishing guide based on the many denizens of Hollywoo. You could have detailed dossiers on Bojack and the main cast, and then branch out to supporting characters, and delving into the show's most important locales -- such as Vigor Enterprises, Bojack's home, the set of Horsin' Around, etc.. At the very least, it would be a great showcase of Lisa Hanawalt's talent as an artist.
In any case, I'm surprised that the creative staff hasn't bothered to publish anything based on this show.